Machine center



Jan. 10, 1933. T. KERR 1,894,101

MACHINE CENTER Filed Jan. 2, 1931 Inventor Thomas Kerr,

His Attorney.

Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE.

THOMAS KER R, F SOHENEC'I'ADY, NEW YORK, .ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION O1? NEW YORK MACHINE CENTER Application filed January 2, 1931. Serial No. 506,170.

The present invention relates to machine tool centers and more particularly to dead centers. 1

In the copending application of Charles F.

5 Marquis, Serial No. 417,209, filed December 28, 1929, there is disclosed a machine center consisting of a spindle or shank of relatively soft metal such as a T nickel steel and a hard, cemented carbide cap or work-engaging portion. The work-engaging cap disclosed in the Marquis application is made by pressing into conical shape a mixed powdered composition consisting of about 87% of a hard metal carbide, such as tungsten carbide,

and about 13% of a binder metal having a lower melting point than the carbide, for example cobalt, or other metal of the iron group. The shaped cap is heated at its sin tering temperature, about 1375 C., in a hydrogen atmosphere and the interior of the bearing cap or cone lapped so as to provide an accurate. fit on the cone-sha d end portion of the soft steel center. he cemented carbide cap is then secured in anydesired manner to the steel center, for example by copper brazing.

The lapping operation performed on. the cemented carbide cap disclosed in the Marquis application requires great care since the cap must be accurately fitted to the soft steel shank. Ordinarily the time required to lap the interior surface of a hard metal cap or cone so as to secure a proper contact between the cap and the soft steel shank may vary from about 6 to 8 hours with a cone having a base about one inch in diameter and an altitude of about one inch.

It is one of the objects of the present invention to provide a machine center with 40 a hard, cemented carbide cap so constructed as to. reduce to a minimum the time required to lap or rind the interior of the cap and secure a c ose contact between the cap and the soft steel center.

The novel features which are characteristic of the resent invention are set forth with articul arity in the appended claims. The invention itself however will best be understood by reference to the following descri tion when considered in connection with tl ie accompanying drawing in which Fig. 1 is a view partly in section and partly in elevation of a lathe center embodying the features of the present invention; Fig. 2 is a perspective view of a cap or cone-shaped member which is adapted to be mounted on a soft steel center; while Fig. 3 is a view partly in section and partly in elevation of a modificatio of the present invention.

In carrying out the present invention, I mix about 97 to tungsten carbide with about 3 to 20% of a metal binder havingxa lower melting point than the carbide, for example cobalt. The mixed powdered materials are pressed in a cone-shaped die or 6 mold under a pressure of about 40 tons to the square inch to form a hollow conicallyv shaped member 1, the inner surface of which is provided with a plurality of integral longitudinally extending ribs 2. After the cap is removed from the die, it is placed in a closed carbon tube and the latter heated about one and one-half hours in a hydrogen atmosphere at a sintering temperature of about 1375 C.

I prefer to employ four ribs each of which I extends substantially the entire distance from the base to the apex of the cone 1. Each rib is provided with a flat bearing surface 3. The sides of each rib 2 diverge slightly so outwardly toward the base of the rib so as v to facilitate separation of the cap and die. Similar points on the different ribs are substantially equally spaced from one another.

The bearing surfaces 3 may be ground 35 with a grinding wheel to provide flat surfaces and the cap 1 then applied to the soft steel center 4, which is preferably a nickel steel containing about 3 nickel. The time required to grind the surfaces 3 is relatively short,-- for example the interior of a. cap having an altitude of about one inch and a base diameter of about one inch may be ound and accurately fitted to a steel shank in about one hour. 9 The bearing cap 1 is secured to the shank or center 4 b any suitable means, for example by copper razing. The cap as pressed in the mold is usually formed with a flange 5. This flange is formed from excess material 100 and may be ground away either before or after applying the cap to the shank or center 4.

In Fig. 3 there is disclosed a modification of the present invention in which the steel shank or center is provided on its conical end portion with plurality of depressions or slots 6 adapted to cooperate with and action in connection with a cemented carbide composition consisting of tungsten carbide and cobalt, it will be clear that the invention is not limited to the particular materials disclosed. Other hard cemented carbides may be employed if desired without departing from the scope of the present invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A machine center comprising a relatively soft metal shank having a conical end portion and a hollow, hard, conical work-engaging member mounted on and secured to said shank, said member having on its inner surface a plurality of ribs adapted to engage the conical end portion of said shank and provide bearing surfaces for said conical member.

2. A machine center comprising a relative- 1y soft metal shank having a conical end portion and a hollow, hard, conical work-engaging member mounted on and secured to said shank, said member having on its inner surface a plurality of longitudinal ribs adapted to engage the conical end portion of said shank and provide bearing surfaces for said conical member, said member consisting substantially of a cemented carbide.

3. A machine center comprising a relatively soft metal shank having a conical end portion and a hollow, hard, conical workengaging member mounted on and secured tosaid shank, said member having on its inner surface a plurality of longitudinal ribs adapted to engage the conical end portion of said shank and provide bearing surfaces for said conical member, said member consisting of a cemented tungsten carbide.

4. A machine center comprising a relatively soft metal shank having a conical end portion and a hollow, hard, conical work-engaging member mounted on and secured to said shank, said member having on its inner sur- ;face a plurality of longitudinal ribs adapted to engage the conical end portion of said shank and provide bearing) surfaces for said conical member, said mem er consisting substantially of tungsten carbide and cobalt varying from about 3 to about 20%.

5. A machine center comprising a relatively soft shank having a conical end portion provided with a plurality of slots therein, a hollow, hard, conical work-engaging member mounted on and secured to saidshank, said member having on its inner surface a plurality of ribs engaging the slots in said shank and providing bearing surfaces for said conical member.

6. A machine center comprising a relatively soft shank having a conical. end portion. said conical end portion having a plurality of longitudinally extending slots, a hollow conical work-engaging member mounted on and secured to the conical portion of said shank, said member having on its inner surface a plurality of longitudinally extending ribs engaging the slots in said shank and providing bearing surfaces for said conical member, and means securing said cap to said shank.

In witness whereof, I have hereunto set my hand this 31st day of December, 1930.

- THOMAS KERR. 

